×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Placement of slab vapor barrier

Placement of slab vapor barrier

Placement of slab vapor barrier

(OP)
I have read several articles about the placement of vapor barriers below a concrete slab. There is some controversy about whether or not concrete should be placed directly on the vapor barrier or should a layer of stone be placed on the vapor barrier first, then the concrete. The slabs we are preparing to place are 4" thick, 4000 PSI concrete, no entrained air, .44 W/C, and approx 20% of the portland type II cement is replaced with ground blast furnace slag cement, #4 rebar each way at 16" on centers. The slabs are approx. 60 feet X 150 feet w/shrinkage joints.

Does anybody know of any serious problems that may be encountered from placement of the concrete directly on the plastic vapor barrier, like maybe slab curling? At this time we are planning on placing the concrete directly on the plastic which is placed over 4" of 57 stone, which is sitting on compacted 2A modified structural fill. At the time the 4" of stone is placed it may or may not be in a covered building.

RE: Placement of slab vapor barrier

Will the slab receive a moisture-sensitive floor covering? If so, ACI 302.1R-96 recommends placing the concrete directly on the vapor retarder. An experienced floor designer recommends keeping the #4 bars 1-in. below the top surface. You may still get some curling, but it's easier (and usually cheaper) to grind curled joints than it is to try to fix a floor moisture problem. For more information on the vapor retarder location question (with pros and ocns for the granular blotter layer) go to www.worldofconcrete.com, Concrete Construction magazine, article archive search. Use "vapor retarder" for the subject and "Suprenant" for the author. For the curling problem enter "curling" and "Holland" for the subject and author, respectively.     

RE: Placement of slab vapor barrier

IAMSSAM, there is a flow chart addendum to ACI 302 where in some cases it is better to put the slab on the vapor barrier and some cases it is better not to.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources